Emilio santuari



April 1, 1924. 1,488,556

E. SANTUARI ARRANGEMENT FOR THE RECOVERY OF ENERGY IN ELECTRICAL RAILWAYSYSTEMS EMPLOYING SERIES CONNECTED DIRECT CURRENT MOTORS Filed Feb; 9.1921 3 Sheets-Sheet 1 5M7, Ania;

April 1, 1924.

' SANT E AR NGEMENT FOR THE Rzcov'ERY '0 TEMS EMPLOYING'SER s con FiFeb. 9, l9

G-Y IN TEDD E ECTRI CAL RAILWAY CURRENT MOTORS I5 Sheets-Sheet 2 Ina 2nfor: [M1150 fmfiun' Apnl 1', 1924. 7 1,488,556

. E. SANTUARI ARRANGEMENT FOR THE RECOVERY OF ENERGY IN ELECTRICALRAILWAY SYSTEIS EMPLOYING SERIES CONNECTED DIRECT"CURRENT MOTORS Filed e1921 3 Sheets-Sheet 5 Patented Apr. l, 1924;

UNITED STATES EMILIO SANTUABI, 0F MILAN, ITALY.

ARRANGEMENT FOR THE RECOVERY ENERGY IN ELECTRICAL RAILWAY SYSTEMSEMPLOYING" SERIES-CONNECTED DIRECT-CURRENT MOTORS.

Application filed February '9, 1921.

To all arr/10m may concern:

Be it known that l, EMILIO SANTUARI, subject. of the King of Italy,residing at Milan, Kingdom otItaly, have invented certain new and usefulImprovements in Arrangements for the Recovery of Energy in ElectricalRailway Systems Employing Series-Connected Direct-Current Motors, ofwhich the following is a specification.

An important considerationin the selection. of the kind of current toheemployed in electrical railway systems having steep grades is thecapacity of the electrical motor equipment tor recovering the greatestpossible part of the energy generated by trains running down hill. hemotors in such a case ct as generators and return current to the supplycircuit. The recovery of energy through the operation ofjan equipment oiseriesconnected direct-current motors has been introduced hitherto inonly a few isolated cases, on account-of the often complicatedconnections which are necessary in order to enable the motors to act asconstantly working genera-tors during the recovery period. Theobjections met with in the systems hitherto employed for recoveringenergy by means of series-connected direct-cin'rent motors are ofvarious kinds; among them may he mentioned:

The necessity of providing'the traction motors with specialshunt-connected generator windings to he used during the recoveryperiod, or alternatively the neces sitv ot independently supplying theseries tield windings of the motors from a separate source i low-voltageenergy, which source of energy may consist of an excitation machine,such as a motoiagenerator set, or

an accumulator hattery.

An excitation machine involves a complicated system in order to make itpossihle to regulate the excitation voltage independently olithe speedof the train.

Whcnan accumnlatm' battery is used for suiiiplying the field windings,the dead weight of the locomotive-or motor coach is C(lllSltlOl'RlJl)increased in view of the .considerahle capacity for which the batteryhas to be built.

All these measures, which, as stated above, are necessary in order thatthe traction motors mm act as genera-tors,v necessitate on the one handa considerable complexity.

Serial No. 443,701.

in the equipment of the cars or coaches and and the cost of theequipment.

It the recovery of energy through the agency of motor cars has never yetbeen effected, this is due principally to lack of space. Indire-ctcurrent higlrtension railway systems, interruptions in operationhave often been experiei'iced, which interruptions were found to be dueto faulty operation otthe driving motors for the excitation generators,these motors heing supplied directly trom the mains with hightensioncurrent. Serious damage to these motors necessarily causes trouble withthe excitation machines and leads to a short circuit. in the motors,which might prove very dangerous both for the motors and for the wholeequipment. On the other hand, the systemot' recovering energy by meansof excitation machines driven ine- 'chanically by the locomotive ormotor car axles is very sensitive in operation. necessitates oneroussupervision and attention and gives rise to constant expense inconsequence of the necessity of providing a complicated automaticregulating device which allows of regulating the voltage of theexcitation generator independently of the speed (oi? thetrain. It theuse of a special separate source of ilow-voltae energy for supplying thefield windings ot the motors during the recovery period is to beavoided, it is neceiaryi accordin to the systems hitherto employed, toprovide a large number otmotors upon a single locomotive or motor car:some of these are utilized. during the recovery period, to excite theremaining;- motors, which generate current to he returned to the mains.Although this method. can heemployed where excessively heavy locomotivesare used, as

is thecase, for example, on American railways, it siunsiutahle torlocomotives which are hnilt torrailways in many other countries. theweight of which is necessarily limited in order not to exceed the axlepressure that is permitted.

By means of the system which forms the subject of the present invention,the

.abovementioned objections are obviated.

During regeneration periods the motors work as shunt-excited generatorsand the current which supplies the tield windings is furnished by themotors themselves.

The invention is based upon the following considerations.

1. The units of the motor equipment form a sort of li heatstouc bridge,the branches or which may consist of separate units or of a group otunits connected together in certain ways.

2. The series field windii of the units, suitably connected together.are further connected to the junctioirpoints of the brie go to which ina ll heatstone bridge, the galvanoineter is connected.

A disturbance of the symmetr of the whole system produced in somesuitable way. Under these conditions, there a ises a diii'erence inpote: tial between the points of otherwise equal potential to which theexcitation current circuit of the motors is connected, and thisdifiei'cnce in voltage creat a current which flows through theexcitation coils of all units in the desired direction.

The accompanying drawings illustrate diagrammati the various embodimentsof the intention, whei iii- Eigure 1 illustrates the il'uudauie in;diagram of the ll heatstone hn L; I

F ig. 2 illustrates the usual wiring diagram of a i our-motor equipment;p

3 illustrates aresistance unit ror causing a disturbance of the symmetr;of: the bridge;

Fig. 4 illustrates the symmetry of the bridge disturbed by means ofreducing the excitation windings of some of the machines Fig. 5illustrates the units disturbed by running the motors at dittei'entspeeds;

Fig. 6 illustrates another method oi counegt ng re sistance units in thecircuits;

i 1g. 1 illustrates the arrangement as in ig. i applied to compoundmachine;

ig. 8 illustrates the diagram simplified. being any suitable excitationcircuit;

Figs. 10, 11 and 12 illustrate the connection tor a six-motor equipment;

rig. 13 illustrates the connections for an eightanotor equipment;

Figs. 14; and 15 illustrate the connections for changing from series toshunt operation of the machines;

Fig. 16 illustrates the connections tor a sixanotor equipment providedwith a re sistanceunit for equalizing the current; and

Fig. 1'? illustrates, the connections for all t the embodiments illusrated in Figs. 3, t,

T, 14 15 and 16.

The reference numerals 1, i2. 3, 4. which illustrate by way of example atour-motor equinment. indicate the armature windings and 5. 6, 7 8indicate the field windings of the motors which, during normal travelare connected in series with the proper armature windings. F or therecovery of energy, the field windings are arranged in series one withanother. and the terminals of the circuit thus formed are connected tothe points N and M. It the group ot' units so connected is connected inthe manner illustrated, to the main source of power. then, if the fourmotors are. as usual, alilze, there will. be a complete symmetricalcircuit. since the points H and N must be of equal potential and noappreciable amount ot' current will flow through the excitation coils.The generated clectrcunotiYe force of the units will therefore, bepractically nil. ll. now the symmetry of the bridge is disturbed by theOIBPlQYI! ent of any suitable means, M and will assume ditlerentpotentials and this will create a ditl'erence in potential which willallow a current to flow through the excitation coils of the machines.

It Fig. 1 is rearranged to cause it to conform to the usual connectiondiagram of motor-coach equipment the arrangement shown in Fig. 2results. In this figure. the only; change in connection is av slightaltera tion of the sequence of the excitation coils. This latterarrangement is adhered to in all the subsequent cases that aredescribed.

The disturbance of the symmetry of the bridge may as stated. he producedin \'l1l'lnus ways. and several methods are explained in detail below.by way of example in connection with a tour-motor equipment.

Fig. 3 hows the first method. The reference numerals 1 to 8 indicate asabove the separate parts of the four main machines. .9 indicates aresistor of suitable capacity and capable ct bciug regulated as desired.which resistor is placed in series with the iozcitation windings ol theuuichiucs. suitziible resistor that is adapted to be suitably regulatedand. if desired. prorided with self-induction: this resistor is arrangedin shunt to the field windings 7 and 6. V

The drawing shows the connections which should be tormed between theseveral windings and resistors during the period of rccorery of energyand are to be obtained by means of special arrangements of controldcvices. Assmning that the four machines are, as usual, alil c and thatthe resistor 10 is f nlhtlltfllllfll, then. alreadv stated, the machineswill not excite themselves and there will be practically a completesyu'h metrical. circuit. Ti, however. the. resistor 10 :ertcd. incircuit and set at a predetermncd value, then the electroinotivc forceproduced in the armature windings 2 and 3 will assume a lower value thanthat in the armature w' idings 1 and aland the potential atpointN willbecome higher than that at 1 The excitation winding are. accordii 7.then trarcrsed by a current. which, in consequence of theabove-described conneclt is a ltlf) rent terist ics.

tions, will excite the "armature windings in the required direction. Theexcitation curroduced during the recovery period shoul traverse thefieldwindings of the machines in the same directionin which it traversesthese windings during. the normal running of the machinesas'series-connected motors. It wlll be seen that the excitation currentproduced in this manner is practically independent of the magnitude anddirection of the main or regenerated current. The machines, connected inthis manner, ac cordingly operate as shunt-excited machines and are,consequently, adapted to operate as generators returning current to themains. In this embodiment of the invention, the symmetry of the bridgeis disturbed by a suitable arrangement of a resistor in shunt to thefield windings of some of the machines, that is to say, by weakening thefield of the latter as compared with the other machines. The same ob'ectcan be obtained in another way by wealiening the field by reason ofreducing the active turns of the excitation windings of some of themachines.

v*Fig. 4 illustrates the principle underlying this method, in the caseof :the above mentioned four-motor equipment. The parts indicated by thereference numerals 1 to 9 are the same as before except that theresistor 10 is omitted. The field windings in dicated by 6 and 7, whichbelong to the machines with the armature 2 and 3, are .provided atsuitable intermediate points with attachment terminals 0 b, which allowthe active turns of these two excitation coils to be reduced. In thisca'se, also, the excitation circuit of the machines is formed by connecting all four excitation coils in series relation, but, by the use ofthe attacl'nncut terminals (1, I), only a part of each of the excitationcoils 6, 7 is rendered active. "ith this method, also, the results maybe obtained that the electromotive force produced in the armaturewindings 2 and 3 is of lower value than that in the armature windings 1and 4 and the potential at N is higher than that at M. In this case,moreover, the sequence of the field windings in the excitation circuitmay be chosen at will, while in the :asc illustrated in Fig. 3, it istixed it' only one resistor is to be used.

A third method of disturbing the symmetry of the bridge is atfordelil bythe use of machines of dili'erent saturation charac- In, this case, themachines do not need attachment terminals on the tie-id windings and theuse of aresistor is also superfluous.

Fig. 5 illustrates an example of this method. The two machinescomprising the armature winding 2 and field winding 6, and the armaturewinding 3 and field w nding], have different saturation values fromthose of the other 1 machines, their saturation the present case, havingthe two resistors 10 and 1.1. The

values being infet'erably higher. The circuit of the excitation coils isformed as before; with regard to the sequence of the several fieldwindings the same selection is available as in the case of Fig. 1. Thefour machines may be excited in any suitable way in the desireddirection and the E. M. F. in the armaturcs of the machines of highersaturation; that is, in the armatures 2 and 3, will be of lower valuethan the E. M. F. in the two other arn'iatures, and, as before, thepotential at N will be higher than that at M. Accordingly, a currentwill flow through the excitation coils in the desired direction and themachines will excite themselves as shunt-connected generators and willcontinue to operate as such.

A further manner of disturbing the symmetry is illustrateddiagrammatically in Fig. 6. In this case, four similar 'maincurrentmachines are used, the armature and field windings of which areconnected as in the foregoing case, with this dif'lerence, that, in thepresent case, the four machines have the same density of saturation. Forobtainingthe desired disturbance of symmetry, there are employed twoadjustable, similar and suitable proportioned resistors 10 and 11, whichare connected in circuit at a suitable point ahead of the armatures 1and 4. lVhen the resistors 10 and 11 are suitably adjust-ed, if thesystem so organized is connected with the mains, then the drop inpotential of the current flowing through the armatures of the machinesin the four branches of the bridge will not be equal but it will attaina higher value in those branches which have a higher resistance; intherefore, in the branches potential in this case will also be higher atpoint N than that at point M.

If? the motor equipment is composed of four machines whic 1, whileotherwise alike, have a diflerent armature resistance, and if thesemachines are connected as shown in -Fig. 6, so that the two armaturcswhich have the higher resistance take the place of elements 1 and 10 orof elements 4 and it, then, in this case, the resistors '10 and 11 aresuperfluous and the same result is obtained without them. 7

A further method of disturbing the symmetry oi the bridge is allorde lby selecting dilterent speeds for othcmvise identical machine-s.Reference may be made to Fig. 5. The four machines are identical withone another. Iii, by any means, the speed o'l. the armatures 1 and l; isincreased as compared with the speed. of the others, then higher E. M.Ffs willv be produced in the armat-ures 1 and i as compared with thosein the arn'iaturcs 2 and Point I? will, in this case, "also have ahigher *potential than 1nd the four machines will thin- 11 l c o. exactas heiore, to .Xcite the1n attained or sel stood without an turthere-;\'p1'a1a11o11 1.e111g necessary. A special is that 111 whu'l 111:.c11111es 1 111111.1ers oi turns in the 11111111- 1112 p .yed: that 1ithcr 1 1 i .1 111d for dili'erent volt siole where two or more "mes,

1e clearly understood tha' the disturl anee in the try oil the bridge111a he produced siniultaneouslv 11 two or more of the methods previouexplained.

The GXL tation curre wroduced in the manner e.:nlained ahove. whichcurrent. as f l stated, is practically inde 1encent ot the magnitude anddirection ot the 11111111 curt. 11111 he controlled 111 various ways.

e11 lhis method makes possible, so, a control of the lo; (1 or speed ofthe machines. The tollowing ditierent. methods of control will heconsidered.

in the first place, the desired control may he etii'ected 13f. varyingthe active resistance of the resistor as indicated in Fig. 3. it will heclearl; understood that, by su1t ahly rarvlng thi.) resistanc the E. M.F.

uduccd in the armature and, consequent ages at windings 2 and 3 I thevalue of the and M may he *aried. manner, the excitation current of theto 1 1' machines may he brought; to the magnitude and the load or speedof incs ma he. regulated to the d sired DOHhb values.

.1 second method is afforded by 'arying the series re. for 9. If, in thearrangement 1llustrated 111 J g. 33, 1t assumed that the disiurha11cc'ii'oduced rosistm' 11,

"stor fl 1 res 1s p 'act1cally independent of the 10:1 d oi the 111chines, the excitation current 111111 1. atod wlthiu. desired limits {11ienly, the load and speed of the and, e nse- 1 1:1cl 1 he VLllQd.

, of regulating the excitation current andv with it the load and speedof the machines by varying the series resistor 9 has been alreadyconsidered in all the illustrated methods of disturbing the synnnetry ofthe bridge and, accordingly, the resistor 9 has been included in Figs. 3to 6.

In the case illustrated in Fig. 1-. the excitation current may also heregulated by disposing ditlcrent attaclnnent terminals or taps on theexcitation coils 6 and T.

- A further method of regulating the ercitation current is by varyingthe resistors 10 and 11 which. in the system of Fig. 0, are connected inthe armature circuits. This method will vary the potential dili'erencebetween the points )1: and N, as well as the excitation current.

Finally, it may he mentioned that the provision of different speeds forthe 111a chines permits of regulating the excitation current, providedthat there are at hand suitable means, such as variable speed transmission and the like, which allow of v:11' v ing the speeds of some ofthe 1111::11i11es. with regard to the others, gradually or 1.1:; stages.

It will be understood that two or more of the above-mentioned methodsfor vary ing the excitation current or for regulating the load and speedof the machines may he used simultaneously. The 11111111 or regenerativecurrent machines, when connected according to the methods explainedabove, operate, in general, as machines excited in shunt, and theirspeed is p 'actieally independent of the load. The machines may, ofcourse, operate either as motors or as gene 'ators. In many vases, and,particula ly, in raih'a work, a purely shunt characteristic ot' themachines undesiri 1110 because the operation of the machines is thenrelativcl inflexible; so tha they are exposed to heavy changes of loadand even to short-circuits, which endanger the 11111- chines themselvesand may throw an undesirable load upon the mains. It is, therefore,preferable to arrange the machines as compound machines. This result111a be attained ver snnplv 11y c3=uneet111g a small part. of theexcitaticn w ding constantly in circuit with the ar1na1'1 .e of themachines. This part of the wini'liug then acts a compound winding.

Such an arrangeiueut as his. lot the lourmotor equipmen illustrated 111Fig. 1. 1s

shown diagrauunalicaliy 1. The reference characters 1 to 9 indicate1111: same parts as hetero hut. in this case, the excitation coils t3, 7and t are each divided into two parts. One part. which indicatedrespectively b 51, 6, T and 8 (corresponding to the respectiveexcitation coils) is a ways connected to its proper arn ature mindingand operates, in the arrangement illustrated as a compound winding. henacting as motors, the machines take current 111 Fia from the mains, andthe compound winding supplements the action of the part of theexcitation coil that is connected in shunt, so that the excitation ofthe machines is strengthened when the motor current rises. In this way,the induced E. M. F. in the armature windings increased and the speed isdecreased so that the load is diminished. lVhen, on the other hand, themachines are acting as generators and are returning current into themains, the compound winding works in opposition to the part of theexcitation coil that is connected in shunt and the excitation is,therefore, reduced when the regenerated current rises. Consequently, theE. M. F. induced in the armature windings is of lower value and thecurrent returned into the mains will be reduced. The result of thisaction is an automatic reduction of the load of the machines.

The fundamental idea on which my invention is based may be utilized inmany ways; the case which has been considered so far of a motorequipment consisting of four machines is only put forward by way ofexample and for the sake of sii'nplicity. In explaining the invention bymeans of further systems, it appears to be desirable to simplify theconnections illustrated hitherto and to unite them in a single diagramof connections. For the sake of simplicity all resistors and the partsof the excitation coils that act as compound windings will be omittedand the excitation circuit will be indicated quite diagrammatically.This is the case in Fig. 8, in which reference figures 1, 2, 3, 4,indicate as before the armature windings of the four machines, while theletter E indicates the excitation circuit, which may be formed in anysuitable way.

Some of the many cases which may occur are considered below. In asix-motor equip ment, for example, the connections indicated in Figs. 9,10, 11, 12 may be made. The reference characters 1, 2, 3, 4, 5, 6indicate the armature windings and E the excitation circuit. M and N areagain the opposite points of the bridge to which the excitation circuitis connected. In Figs. 10 and 11, it will be noted that the bridgeembodies the armature windings 3, at, 5 and 6 only. In Fig. 10, thepoints P and Q are short-circuited and in Fig. 11 the armature winding 5is connected at point P with the armature windings 2 and. 4.

In all the examples that have been considered hitherto, the excitationcoils of all the machines are connected in a single series circuit.Cases may, however, arise as indicated in Fig. 12, in whichtheexcitation circuit is formed of two or more groups in parallel relation,each comprising a plurality of series-related excitation coils. Finally,the excitation circuit may be formed by suitable series connection ofseparate elements comprising excitation coils which vary amongthemselves in the number of parallelconnected branches.

Connections arealso possible as indicated in Fig. 13, in which only aportion of the machines are used for generating the excitation current.In this case, which illustrates one of the many possible arrangements ofan eight-motor equipment, the reference characters 1 to 8 indicate thearmature wind ings of the machines. E indicates the excitation circuit,which may be formed in any suitable way from the whole of the excitationcoils, and M and N indicate the points at which this circuit isconnected. As may be seen, the armature windings 1 and 2 do not assistin creating the excitation current.

In equipments with more than four motors, the number of possibleconnections considerably increases, but it is not necessary to considerthese more closely. In general, two machines which lie in oppositebranches of the bridge and are accordingly excited equally and loadedequally, may be replaced by a single machine, the armature of which hastwo independent windings that lead to two commutators. For disturbingthe symmetry of the bridge, the regulation of the excitation current,the production of the compound operation and the possibility of variousconnections with more than two double-commutator machines, the sameapplies as has been said already with regard to machines having singlecommutator.

By way of example, there is illustrated in Fig. let the arrangementpreviously shown in Fig. 2 and also containing the last-namedmodification. Here the armature windings 2 and 3 and the field windings6 are illustrated on one side, since they form a single machine. In likemanner are treated also the armature windings 1 and 4 and the fieldwinding 5, which form the other machine.

It is clear that just as a certain number of machines with a. singlecommutator can be replaced by half the number of double commutatormachines, so also can half the number of twin machines be arranged inplace of the full number of single-commutator machines.

Hitherto, the normal operation of the ma chines operating according tothe present invention has been considered. A method will now be brieflyconsidered that renders possible an easy transition from the normalseries operation to the shunt or compound operation of the machines, inthe simplest possible form. The basis of this method is indicated inFig. 15, for example, in connection with the already mentioned fourmotorequipment. In Fig. 15, the four branches of the bridge are indicatedrespectively by the reference characters I, II, III and IV.

First of all, some of the machines are cuit ii ages of the armaturewindings of the machines working idly in the two open b anches (in 15the armature windings l and 4:) are next increased as 01111): red

wit h those oi the a mature windings which are carrying current (in Fig.15 the armature windings 3 and 2) so that, when the bridge in s beenformed by closing the switches l0 and ii, the necessary disturbance thesymmetry of the bridge has been already effected, to thus obtain theoperation of the machines as shunt or compound machines. The regulationof the voltage may be eilected by means of any or the methods al eadydiscussed that serve for disturbing the symmetry of the bridge. \Vhenthis variation oi? the voltages has taken place, the necessaryregulation mi be ell'eeted with the resistor 9 until there is no longerany difference in potential on opposite sides of the switches 10 and 11,that is, between the points a and Z), or c and (Z. T he switches to andti are then closed and transition take. place from series to shunt orcompound operation of the machine without violent fluctuations ofcurrent.

These methods may be to any possible applied in the same way connectionboth with singlerommutator and with doubleconrnutator or twin machines.

It the i IOH branches of the bridge, com- Jin either single machines orgr up of nines. are adapted for the same strength as is the case, forexample, in and 11, then the machines will unequally loaded in shunt orcompo i 1 under all conditions. This statement may be explained with thehelp of i n. tor erample. Suppose that the four machines are adapted torthe same strength of current and the letters J J J J and J respectively,indicate the currents in the four armature windings and in the commonexcitation circuit. If the machines are operating as generators supplying energy to the mains, the armature currents take the directionsindicated. The excitation current J flows in the direction of the cor'esponding arrow. Then J .LJ., a 1d J :J J under all conditions; that isto say, the armature currents in two branches connected in seriesrelation always vary by an amount corresponding to the excitationcurrent; or. in other words, by the current flowing in the shunt circuitbealway 5 un d o )erat tween M and N. In p ac-tire, it will in attempted, in general, to make J -l and it will be seen, therefore, thatthe armature coils l and i, when ihe machines are operated asgenerators, are always more heavily loaded by the amount oi theexcilation current than the armature windings 2 and in the latterarniatures, the current 11122:! assume a zero Value or eren a negativevalue, even when the equlpnris acting regeneratively (in this case twonuichines in question will then be running as motors), it the excitationcurrent reaches a very high yalue. it is desirable, therefore toequalize the loads of the n'laehines by providing in the more heavilyloaded branches 1 and 1V mac iines that a e adapted 'l'or greater ru renstrengths. or several like machines connected in parallel relation toone another. The latter method, ior example. has been utilized in thesvstein 01 Fig. 2'). in this case, the branche .l. and IV are eachformed of two like n'iachines connected in parallel relation, while thebranches ii. and Ill comprise single niachines.

In this case, which is given by way of example, a complete equalizationof loads on the machines is obtained it the current flowing in theexcitation circuit, or more correctly in the shunt circuit between thepoints M and N, is equal to a third of the current that is returned tothe mains; that is to say, if the excitation current is equal to thetrue armature current of each machine.

As soon, however, as the current in the excitation circuit becomes lowerthan third oi the main current. the reverse action to what is shown inFig. 8 in this connection occurs: the machines operating in the branchesIII and II are loaded more than the others.

Thus, in order to equalize the load of the machines, the current in theshunt circuit is increased and is made equal to a third o'lJ themaincurrent. The excitation current must. of course. remain cluinged. Thesaid eqr alization may be very easily effected by introducing a variableresistor, which may be provided with self induction, in shunt to theentire .xcitation circuit. .An example is shown in Fig. 16, whichillustrates the method of equalizing the load for the six-motorequipment shown in Fi 9.

The letter R here indicates an adjistable resistor. which may beoperated in any suit able manner-by hand. mechanically. clertrically orautomatically by a relay (0. a. a differential relay). This resistor isalw: set so that the current in the shunt excitation circuit is equal toa thiro ot the main current. The above-mentioned equalization of the load of all machines will. then be effected. in a corresponding manner, itis also ])(..-I-

Hill

plied to a single system as shown diagramn'iatically in l ig. 17. Thesame reference characters are used as those used in the other figuresexcept that 5", 6", 7 and 8 indicate the i'ield windings and 5, 6", T,and 6 indicate the adjustable exciting coils. l3 and 14 indicate twosuitably proportioned and adjustable resistors and are in seriesrelation with switches 11 and 12.

To sum up, the system forming the subject of the present inventionaffords the fol- J owing advantages:

1. Simplicity, since it makes possible the recovery of energyexclusively by the use of the railway motors without any additional apmratus; it is, therefore, adapted to be used also on motor coaches.

2. A reasonable adaptation of the characteristic of the motor equipmentto the requirements of the line.

3. Independence of the excitation current with respect to the directionof the main current.

4;. The possibility of obtaining from a series-connected motor equipmenta shuntconnected or group operation by simple means.

5. Stability of operation of the machines whether operating as motors oras generators.

6. Easy and gradual regulation, of the several stages of speed.

7. A more reasonable utilization of the machines.

Having now particularly described. and ascertained the nature of my saidinvention, and in what manner the same is to be performed, I declarethat what I claim is:

'1. In combination, feed lines; a plurality of dynamo electric machineshaving their armatures arranged in two sets, each set mmprising aplurality of armatures conuected'in series and the two sets being connccted to the feed lines in parallel; exciting coils for the armature'sof said machines arranged in series and connected across the armaturecircuits at points where the potential drop in each set is substantiallythe same; and means whereby a difference in potential drop is caused toexist at the points of such connection of the exciting coils to thearmatures.

2. In combination, feed lines; a plurality of: dynamo electric machineshaving their armaturcs arranged in two sets, the armatures in each setbeing connected in series and the two sets being connected to the feedlines in parallel; exciting coils for the armatures of said machinesarranged in series and connected across the armature circuits at pointswhere the potential drop in each set is substantially the same; andmeans comprising a variable resistance for causing a diflierence inpotential drop to exist at the points of such connection of the excitingcoils to the armaturesand for permitting said difference to be varied.

8. In combination. feed lines; a plurality of dynamo electric machineshaving their armatures arranged in two sets, the armatures in each setbeing comiected in series and the two sets being connected to the feedlines in parallel exciting coils for the armatures of said machinesarranged in series and connected across the armature circuits at pointswhere the potential drop in each set is substantially the same; otherexciting coils arranged in series with the armatures; and means wherebya difference in potential drop is caused to exist at the points 01 suchconnection by the first-named exciting coils to the armature.

i. In combination, feed lines; a plurality of dynamo electric machineshaving their armatures arranged in two sets, the armatures in each setbeing connected in series and the two sets being connected to the feedlines in parallel; exciting coils for the armatures of said machinesarranged in series and connected across the armature circuits at pointswhere the potential drop in each set is substantially the same; otherexciting coils for said armatures, arranged in series therewith; andmeans comprising a variable resistance for causing a difference inpotential drop to exist at the points of such connection of thefirst-named exciting coils to the armatures and -for permitting saiddifference to be varied.

5. In combination, feed lines; a plurality of dynamo electric machineshaving their armatures arranged in two sets,-the armatures in each setbeing connected in series and the two sets being connected to the feedlines in parallel; and exciting coils for the armatures of said machinesarranged in series and connected across the armature circuits at pointswhere the potential drop in each set is substantially the same, certainof said exciting coils being adapted to have portions cut out to cause adili'erence in potential drop to exist at the points of such connectionof the exciting coils to the armatures.

6. In combination, feed lines; a plurality of dynamo electric machineshaving their armatures arranged in two sets, the armatures in each setbeing connected in series and the two sets being connected to the feedlines in parallel; exciting coils for the armatures of said machinesarranged in series and connected across the armature circuits at pointswhere the potential drop in each set is substantially the same, certainof said exciting coils having portions adapted to be two StzLS heingconnected lines in parallel; exciting coils for tl e armatures of saidmachines ar 'anged in series and col iected across the armature circuitsat points where the potential drop in each set is suhstantiallv thesame. certain oi? said coils hai'ing portions adapted to he cut out tocause a diti'ercnce in potential drop to exist at points oi" suchconnection ot tne exciting coils to the armature; other excitiing coilsarmatures arranged in se ries with the same: and means comprising 1variable resistance in the circuit of salt irst-named ex r iting coilsfor further \'ar g such dinerence in potential (li'( lncoinhinatiointeed lines; a p of dynamo electric machines havingarmatures arranged in two sets. the armatures in each set heingconnected in series and the two sets heing connected to the. "teed linesin parallel: exciting coils tor the atarranged in serie iuralit i' Itheir niatnres of said machines and connected acr ss the at points where"l ioten 'tttl drop in cart I X l set is sulstantial the same: and meansesistance arranged in 1 com irisin a var r M w A,

. a said exciting coils tor cau ing a c 11 potential drop to is at thepoints oi such connection ot the. t iting coils to the arinatnres andtor pcr mi ting said difference to be varied.

t 1n eoinhina ion, teed lines; a plurality' of dynamo electric machineshaving their armatnrcs arranged in two sets. the. arniatnres in ea hst-t heing connected in series and the two being connected to the let-dlines in pa 'allel; exciting coils for the arr titres oi" aid machinesarranged in set and connected across the armature circuits at pointswhere a potential ditl't-rence is caused to exist and means comprising avariahle resistance placed in series with ccrtain of said exciting coilsto ca the current therein.

10. In combination. feed line a plurality of dynamo electric machineshaving their armatures arranged in two sets, the armatures in each setbeing connected in series and the two sets being connected to the feedlines in 3121; llel; exciting coils for the armatures of said machinesar anged in series and conn ctied across the armature circuits at pointswhere a potential diil'erence caused to exist; a Y; riahle resistan :e

L t connected across the armature circuits points where the potentialdrop in each. set is suhstantially the same; other exciting ccils torsaid armatures arranged "A. series '1 the same; and a variableresistance ilaced ia shunt with the first-named excitg coils tor causinga ditt'erence in potein 'ial drop to exist at the points of suchconnection ot the exciting coils to the ttl'liltb tures.

In combination, teed lines; a plurality ot dynamo electric machineshaving their arniatures arranged in two sets, the armatnrcs in each setbeing connected in series and the two sets hcing connected to the feed.lines in parallel; exciting coils tor the armaturcs of said machinesarranged in series and connected across the armature circuits at pointswhere the potential drop in each set is snhstantially the same certainot said exciting coils being adapted to have portions cut out to cause adill'erence in potential drop to exist; at the points of such connectioiof the exciting coils to the armatnres; and means comprising a variablereance placed. in series with said ex 'iting coils to control thecurrent therein.

123. in coinhination teed lines; a plurality ol dynamo electric machineshaving their armatures arranged in two sets. the armatures in each setheing connected in series and the two sets heing connected to the feedlines in parallel; exciting coils for the armatures oi said nnu-lrinesarranged in series and connected across the armature circuits at pointswhere the potilillitll drop in cach set is snlaitntially the sonic.certain o'l" said exciting tt heing adapted to have portions cut out tocause a ditl'erence in potential drop to exist at the points oi? suchconnection ot the exciting coils to th armatares; and means comprising a'ariahle resistance placed in shunt with certain oi said exciting coilsfor further varying said difference in potential drop.

14;. In combination, teed lines; a plurality of dynamo electric machineshaving their armatnres arranged in two sets, the armatures in eachsetheing connected in series and the two sets heing connected to thefeed incs in parallel; exciting coils tor the armanres of said machinesarranged in series ill) lUl)

and connected across the armature circuits at points where the potentialdrop in each set is substantially the same, certain of said excitingcoils being adapted to have portions cut out to cause a difference inpotential drop to exist at the points of such con-- nection of theexciting coils to the armatures; and a variable resistance placed inseries with said exciting coils and a variable resistance placed inshunt with certain of said coils for further varying the difference inpotential drop.

15. In combination. feed lines; a plurality of dynamo electric machineshaving their armatures arranged in two sets, the armatures in each setbeing connected in series and the two sets being connected to the feedlines in parallel; exciting coils for the armatures of said machinesarranged in series and connected across the armature circuits at pointswhere the potential drop in each set is substantially the same; andmeans comprising variable resistances placed be tween the tecding linesand the armatnres for causing a diti'erence in potential drop to existat the points of such connection with exciting coils to the armatures.

16. In combination, feed lines; a plurality of dynamo electric machineshaving their armatures arranged in two sets, the armatures in, each setbeing connected in series and the two sets being connected to the feedlines in parallel; exciting coils for the arma tures of said machinesarranged in series and connected across the armature circuits at pointswhere a potential difference is caused to exist; and a variableresistance placed in series with the exciting coils to control thecurrent therein; and variable resistances laced between the armaturesand the feed lines for controlling said potential difler encc at thepoints of such connection of the exciting coils to the armatures.

17. In combination, teed lines; a plurality v of dynamo electricmachines having their armatures arranged in two sets, the armatures ineach set being connected in series and the two sets being connected tothe feed lines in parallel; exciting coils for the armatures of saidmachines arranged in series and connected across the armature circuitsat points where the potential drop in each set is substantially thesame; and a variable resistai'ice placed in series with said excitingcoils and another variable resistance laced in shunt with certain ofsaid coils or causing a difference in potential drop to exist at thepoints of such connection of the exciting coils to the armatures and forvarying said difference; and variable resistances placed between thearmatures and the feed lines for further varying said difterence inpotential drop.

18. In combination, feed lines; a plurality of dynamo electric machineshaving their armatures arranged in two sets, the armatures in each setbeing connected in series and the two sets being connected to the feedlines in parallel; exciting coils for the rinatnres of said machinesarranged in series and connected across the armature circuits at pointswhere the potential drop in each set is snbstantially the same, certainoi said coils being adapted to have portions cut out to cause adifference in potential drop to exist, at the points of suchconnectionot the coils to the arinatures; and a variable resistanceplaced between the armatures and tlie'i'eed lines for further varyingsaid difference in potential drop.

19. In combination, feed lines; a plurality of dynamo electric machineshaving their armatures arranged in two sets, the armatures in each setbeing connected in series and the two sets being connected to the feedlines in parallel; exciting coils for the armatures of said machinesarranged in series and connected across the armature circuits at pointsWhere the potential drop in each set is substantially the same, certainof said coils being adapted to have portions out out to cause aditlerence in potential drop to exist at the points of such connectionof the exciting coils to the armatures; a variable resistance placedbetween the armatures and the feed lines for further varying saiddifiterence in potential drop; and a variable resistance placed inseries with the exciting coils and a variable resistance placed in shuntwith certain of said exciting coils for further varying the difierencein potential drop.

20. ,In combination, feed lines; a plurality of dynamo electric machineshaving their armatures arranged in two sets, the armatures in each setbeing connected in series and the two sets being connected to the feedlines in parallel; exciting coils for the armatures of said machinesarranged in series and connected across the armature circuits at pointswhere the potential drop in each set is substantially the same, certainof said coils being adapted to have portions cut out to cause adifference in potential drop to exist at the points of such connectionof the exciting coils to the armatures, a variable resistance placedbetween the armatures and the feed lines for further varying saiddifi'elence in potential drop; a variable resistance placed in serieswith the exciting coils and a variable resistance placed in shunt withcertain of said coils for further varying the dilference in potentialdrop; and auxiliary exciting coils placed in series with the armatures.

21. In combination, feed lines; a pair of sets of dynamo electricmachine armatures each set connected together and to the feed in proaidpower circuit, which consists 'd potential difierence;

means for Varying Sal connected to two of said terminal points; a secondset of translating devices connected between the remaining terminalpoints; and in means for effecting a drop in potential between thelast-namecl terminal points.

In testimony whereof I affix my signature.

EMILIO SANTUARI.

